a: The angles sum to form a line. Therefore x + y + z = 180 degrees. x = 3y and 3z = 5x. Substitute for x into z. 3z = 15y. Then go back to x + y + z = 180, substitute in the values for x (3y), y and z (5y), and solve. The equation can be solved in any of the variables, y is just convenient. Then go back to the definitions and calculate x and z from y.

b: Solve similarly to a, but in this case the angles sum to a circle, so a + b + c + d + e = 360 degrees. The remainder of the solution is as above.

b: Solve similarly to a, but in this case the angles sum to a circle, so a + b + c + d + e = 360 degrees. The remainder of the solution is as above.